The Nuclear Regulation Authority released Friday the results of a computer simulation on how the use of iodine tablets by people around nuclear plants can protect their thyroids from excessive exposure to radiation in the event of a severe catastrophe.
The NRA’s estimate, compiled by the government-affiliated Japan Atomic Energy Agency, shows that taking iodine before large fallout is released would have a positive effect, particularly for people within 30 km of a crippled plant.
The Japan Atomic Energy Agency also recommended that people within 5 km of a plant evacuate immediately in the event of a disaster and not wait until radioactive materials actually start to escape.
The agency reported its assessment to a panel set up under the NRA in hopes it will help local governments craft effective disaster mitigation plans based on guidelines compiled since the Fukushima crisis started.
The guidelines feature special disaster preparations for people living within 30 km of a nuclear facility. The analysis is based on the assumption that a 1.1 million kw reactor releases radioactive substances at around the same level as those seen in the Fukushima meltdowns.
In its model, a massive radiation leak starts 27 hours after an emergency occurs at a plant and lasts for seven hours.
The amount of radiation affecting people 5 to 30 km radius from the plant could exceed International Atomic Energy Agency criteria for taking thyroid protection — 50 millisieverts in the first seven days — even if they stay indoors for two days before evacuating beyond the 30-km line. But when taking iodine pills 12 hours before the release of radioactive substances, their exposure is expected to drop below the benchmark line.